Hepatitis C virus (HCV) incidence among people who inject drugs declined rapidly after national scale-up of harm reduction interventions such as syringe exchange in Scotland, according to a report published in the August 11 edition of PLoS ONE. Changes in HCV prevalence, however, are lagging behind.

Blood-borne viruses such as HCV, hepatitis B virus, and HIV are transmitted through shared needles, syringes, and other drug injection equipment, and people who inject drugs have high rates of these infections worldwide. Several cities in the U.S., Europe, Australia, and Canada have had success in reducing HIV and viral hepatitis rates through harm reduction programs.

Norah Palmateer from the Blood-borne Viruses and Sexually Transmitted Infections Section of Health Protection Scotland and colleagues examined the potential impact of changes in HCV transmission among people who inject drugs in Scotland, where government policy recently instituted more widespread harm reduction interventions including providing injecting equipment (including needles/syringes, filters, and spoons) and opiate substitution therapy (such as methadone).

The researchers used a framework to "triangulate" different types of evidence at both the group-level and the individual-level. Group-level or ecological analyses examined changes in intervention provision, self-reported intervention uptake, self-reported risk behavior, and HCV incidence (new infections). Individual-level analyses investigated relationships within the pooled survey data.

The authors mainly used evidence from behavioral cross-sectional surveys of nearly 8000 drug injectors conducted during 2008-2012. Most (nearly 75%) were men, the mean age was approximately 35 years, and they had been injecting drugs for 11 years on average.

The researchers focused on recent infections, that is, people who were in the 1-2 month "window period" when HCV is detectable in the blood but the body has not yet produced enough antibodies to register on a standard screening test. They also looked at service data from syringe exchange and opiate substitution programs and facilities.

Results

HCV incidence declined from 13.6 new infections per 100 person-years during 2008-2009 to 7.3 per 100 person-years during 2011-2012.

This finding was supported by reduced hepatitis C prevalence among people who recently started injecting drugs.

Over this period the number of people covered by needles/syringe exchange provision remained stable, while there were increases in the proportion receiving other injection equipment (from about 23% to 70%) and opiate substitution therapy (from 50% to 64%).

There were also decreases in the frequency of daily drug injecting (from 63% to 49%), sharing needles/syringes (from 15% to 8%), and sharing other injection equipment (from 42% to 20% for spoons and from 33% to 17% for filters).

Service provider data showed that the proportion of drug injectors with adequate access to needles/syringes rose from approximately one-half to three-quarters.

In a multivariate analysis, providing needle/syringe and other injection equipment were both associated with reduced risk of recent HCV infection.

Uptake of opiate substitution therapy alone was not significantly associated with reduced HCV incidence, however, perhaps due to insufficient power to detect an effect.

"We estimate the combination of harm reduction interventions may have averted 1400 new HCV infections during 2008-2012," the study authors concluded. "This is the first study to demonstrate that impressive reductions in HCV incidence can be achieved among [people who inject drugs] over a relatively short time period through high coverage of a combination of interventions."

"Our analyses confirmed that opiate substitution therapy was associated with a reduced frequency of injecting, and that lower frequency of injecting was associated with less sharing of all types of equipment," they added in their discussion. "From the unadjusted incidence, it appeared that opiate substitution therapy had a larger effect among those [with] low coverage of needles/syringes and paraphernalia, which would be expected, given that the impact of injecting frequency on HCV transmission would be augmented if insufficient sterile equipment was being used."

"Although we have observed encouraging signs in the direction of HCV incidence, we have not seen any changes in HCV prevalence," the researchers noted. "A mathematical modeling study has suggested that high coverage levels of both opiate substitution therapy and needle/syringe provision would need to be sustained for a 15-year period in order to reduce prevalence by a third. Thus, it may be the case that it will take many years of a sustained reduction in HCV transmission before any changes in prevalence are observed."

9/4/14

Reference

NE Palmateer, A Taylor, DJ Goldberg, et al. Rapid decline in HCV incidence among people who inject drugs associated with national scale-up in coverage of a combination of harm reduction interventions. PLOS ONE9(8):e104515. August 11, 2014.